SPDIF was never built into the Xbox 360 as far as I can remember. It was always on the AV adapter. It never had component out on the box.

Yes, it was.

Xbox 360 Component cable; included in every Xbox 360 sold at launch. Microsoft's favourite catchphrase at the time was "the only console to launch with an HD cable included", making reference to Wii and PS3 composite only cables. It wasn't until the Wii U launched an HDMI cable was included with any console.

The HDMI HD adapter wasn't released until the Elite launched. As you can see, it still has the 40 pin connector, so absolutely impossible to use with the Component cables etc. HDMI cable + adapter only.